#include <Wire.h>

#define SLAVE_ADDR 0x77
#define BAUDRATE   38400

uint8_t busyFlag = 0 ;  // 0-Ready : 1-Busy
char    buf[64];

void i2c_receive(int numBytes)
{
	char *pt = buf;
	while (Wire.available()){
		*pt = Wire.read();
		pt++;
	}
	busyFlag = 1;
	*pt = 0x00;
	Serial1.print(buf);
	busyFlag = 0;

}

void i2c_send()
{
	Wire.write(busyFlag);
}

void setup()
{
	Serial1.begin(BAUDRATE);
	Wire.begin(SLAVE_ADDR);

	Wire.onReceive(i2c_receive);
	Wire.onRequest(i2c_send);

	Serial1.write("I2C SLAVE STARTED\n");
}

void loop() {}

#include <Wire.h>

#define SLAVE_ADDR 0x77

void debug_print(const char* format, ...)
{
	va_list args;
	char buf[256];
	va_start(args, format);
	vsprintf(buf,format,args);
	va_end(args);

	Wire.beginTransmission(SLAVE_ADDR);
	Wire.write(buf);
	Wire.endTransmission();
}

void setup()
{
	Wire.begin();

	debug_print("Date : %04d/%02d/%02d %02d:%02d:%02d\n",2023,7,4,14,9,20);
}

void loop() {}